JP2010121089A - Rubber composition and tire using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition capable of exhibiting excellent processability while preventing reduction of a rubber physical property by using a natural rubber enhancing processability without reducing the physical property inherently possessed by the natural rubber and a vulcanization promoter having a vulcanization delaying effect equal to or more than DCBS without using a vulcanization retarder such as CTP having possibility that a problem of blooming or the like is generated, and a tire using this. <P>SOLUTION: The rubber composition contains a rubber component containing the natural rubber obtained by performing deproteination treatment of a natural rubber latex such that a total nitrogen content in the natural rubber is adjusted to 0.12-0.30 mass%, a sulfenamide-based vulcanization promoter represented by formula (I), and a sulfur. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition containing a specific natural rubber and a sulfenamide-based vulcanization accelerator and capable of exhibiting excellent processability, and a tire using the rubber composition.

  It is desired that rubber compositions used for tires for passenger cars, trucks, buses, motorcycles and the like have various high physical properties. As a rubber component of such a rubber composition, natural rubber excellent in mechanical properties, low heat build-up, and wear resistance is often used. However, the processability of natural rubber is generally inferior to that of synthetic rubber. This is because the entanglement of polymer molecules increases through the polypeptide bond contained in the protein present in the non-rubber component of the natural rubber latex that is the raw material, the apparent molecular weight becomes very large, and the Mooney viscosity of the rubber increases. It is to bring about.

  Conventionally, in order to improve the physical properties of such natural rubber, for example, as disclosed in Patent Documents 1 to 3, removal of non-rubber components has been performed. However, these remove the protein almost completely, and at the same time, the non-rubber component having an anti-aging action and a vulcanization accelerating action is almost completely removed. In order to improve these points, natural rubber subjected to a specific treatment has been developed (see Patent Document 4).

  On the other hand, a sulfenamide vulcanization accelerator that contributes to improvement of physical properties such as adhesion is particularly useful as a vulcanization accelerator indispensable when producing rubber products such as tires. Among the commercially available sulfenamide-based vulcanization accelerators, examples of the vulcanization accelerator that gives the slowest effect to the vulcanization reaction include N, N′-dicyclohexyl-2-benzothiazolylsulfene. Amides (hereinafter abbreviated as “DCBS”) are known. Furthermore, when slow action is required, a sulfenamide vulcanization accelerator and a vulcanization retarder such as N- (cyclohexylthio) phthalimide (hereinafter abbreviated as “CTP”) are used in combination. Things are also done.

JP-A-8-143606 JP 11-714078 A JP 2000-19001 A Japanese Patent No. 373296

  However, even when natural rubber subjected to a specific treatment as described above is adopted, when used in combination with a conventional vulcanization accelerator, the Mooney viscosity rises more than necessary, and a good kneading operation tends not to be realized. It is considered difficult to secure a suitable Mooney scorch time at the same time. Further, when the vulcanization retarder as described above is used in combination, depending on the amount of the vulcanization retarder, the physical properties of the vulcanized rubber may be adversely affected, and the appearance and adhesion of the vulcanized rubber may be deteriorated. A problem arises that causes blooming that adversely affects sex.

  Therefore, the present invention does not use natural rubber with improved processability without deteriorating the properties inherent to natural rubber and a vulcanization retarder such as CTP that may cause problems such as blooming. The present invention provides a rubber composition capable of exhibiting excellent processability while preventing deterioration of rubber physical properties by using a vulcanization accelerator having a vulcanization delay effect equal to or higher than that of DCBS, and a tire using the rubber composition The purpose is that.

  In order to solve the above-mentioned problems, the present inventor has found a rubber composition using a natural rubber subjected to a specific treatment and a specific vulcanization accelerator in combination, and has completed the present invention.

  That is, the rubber composition of the present invention is a natural rubber obtained by deproteinizing natural rubber latex, and the total nitrogen content in the natural rubber is 0.12 to 0.30% by mass. It is characterized by containing a rubber component containing an adjusted natural rubber, a sulfenamide vulcanization accelerator represented by formula (I), and sulfur.

(In formula (I), R ¹ represents a branched alkyl group having 3 to 12 carbon atoms, and R ² represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. Represents 0 or 1, and x represents 1 or 2.)

The natural rubber is preferably obtained by coagulating the natural rubber latex after the deproteinization treatment without centrifuging the non-rubber component, followed by drying treatment, and the Mooney viscosity (ML _{1 + 4} ) of the rubber. It is desirable that the stress relaxation time (T ₈₀ ) satisfies the following formulas (A) and (B).
40 ≦ ML _{1 + 4} ≦ 100 (A)
T ₈₀ <0.0035exp (ML _{1 + 4} /8.2)+20 (B)
[Where ML _{1 + 4} is the Mooney viscosity measured value at 100 ° C., T ₈₀ is the time (seconds) required to stop the rotor rotation immediately after ML _{1 + 4} measurement and the ML _{1 + 4} value is reduced by 80%. ). ].

The sulfenamide vulcanization accelerator is preferably contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component, and 0.3 to 10 parts by mass of the sulfur. It is preferable to contain by quantity.
In the formula (I), R ¹ may be a tert-alkyl group, n may be 0, R ¹ is a tert-alkyl group, and R ² is a linear alkyl having 1 to 6 carbon atoms. It may be a group or a branched alkyl group having 3 to 6 carbon atoms.
Furthermore, the rubber component desirably contains polyisoprene rubber, and may contain 5% by mass or more of the natural rubber in 100% by mass of the rubber component.
The tire of the present invention is characterized by using these rubber compositions for tire members.

  According to the rubber composition of the present invention, a natural rubber having improved processability while maintaining good physical properties inherent to natural rubber, and a vulcanization accelerator having a vulcanization retarding effect equivalent to or better than DCBS are used in combination. Therefore, an increase in Mooney viscosity is effectively suppressed, the kneading operation becomes easy, and an appropriate Mooney scorch time can be maintained. Further, since there is no need to use a vulcanization retarder such as CTP which may cause problems such as blooming, there is no possibility of adversely affecting the physical properties of the vulcanized rubber. Therefore, a rubber composition that exhibits excellent processability while maintaining good rubber properties can be obtained by the synergistic effect of these natural rubber and vulcanization accelerator.

  Therefore, if the rubber composition is used, a high-performance tire can be easily obtained by such excellent processability.

Hereinafter, the present invention will be described in detail.
The rubber composition of the present invention is a natural rubber obtained by deproteinizing natural rubber latex, and is adjusted so that the total nitrogen content in the natural rubber is 0.12 to 0.30% by mass. It is characterized by containing a rubber component containing natural rubber, a sulfenamide vulcanization accelerator represented by formula (I), and sulfur.

[Natural rubber]
The natural rubber used in the present invention is obtained by adjusting the total nitrogen content to be 0.12 to 0.30 mass% by deproteinization treatment of natural rubber latex. The natural rubber latex used as a raw material is not particularly limited, and a field latex, a commercially available latex, or the like can be used.

  Deproteinization of natural rubber latex can be performed by a known method. For example, a decomposition treatment method using an enzyme, a method of repeatedly washing with a surfactant, a method of using an enzyme and a surfactant in combination, a transesterification method using sodium methoxide, sodium hydroxide, potassium hydroxide, etc. There is a saponification method using

  As the enzyme, a protease, a peptidase, a cellulase, a pectinase, a lipase, an esterase, an amylase, etc. can be used alone or in combination. The enzyme activity of these enzymes is suitably in the range of 0.1 to 50 APU / g.

  The amount of proteolytic enzyme added is suitably 0.005 to 0.5 parts by weight, preferably 0.01 to 0.2 parts by weight, based on 100 parts by weight of the solid component in the natural rubber latex. is there. If the amount of proteolytic enzyme added is less than the above lower limit, the protein degradation reaction may be insufficient. If the amount exceeds the upper limit, deproteinization will proceed excessively, resulting in a balance between the desired processability and physical properties. You may not be able to remove.

  In the present invention, when performing the proteolytic treatment, a surfactant may be added together with the proteolytic enzyme. As the surfactant, an anionic, cationic, nonionic, amphoteric surfactant and the like can be added.

  In the present invention, the total nitrogen content in the latex solid content is adjusted to 0.12 to 0.30% by mass, preferably 0.18 to 0.25% by mass, by the above deproteinization technique. Is needed.

This nitrogen is derived from the nitrogen of the polypeptide bond. Determination of polypeptide binding may be performed by measuring the absorbance at 3280 cm ^-1 by a polypeptide bond proteins by infrared spectroscopy. Here, the total nitrogen content of 0.12% by mass means that the polypeptide bonds are decomposed by almost 80%. Moreover, the total nitrogen content of 0.30% by mass means that the polypeptide bonds are decomposed by about 20%.

When the total nitrogen content is within the above range, there is no risk of deterioration of physical properties such as mechanical properties and anti-aging properties, and the rubber viscosity is appropriately reduced by the decomposition of the peptide bond, and a Mooney viscosity with a suitable value is obtained. A rubber composition having the same can be obtained. Further, when a filler such as atomized carbon black is further blended, it contributes to an increase in the interaction between the filler and the rubber, and the dispersibility of the filler in the rubber can be improved. On the other hand, when the upper limit is exceeded, workability may be inferior.
The polypeptide degradation rate is preferably 20 to 80%, particularly preferably 30 to 70%.

  The natural rubber latex deproteinized as described above is preferably coagulated without separating non-rubber components. When non-rubber components are separated, rubber properties such as anti-aging properties may be inferior. Next, the natural rubber used in the present invention can be obtained by washing the obtained rubber component and then drying it using a normal dryer such as a vacuum dryer, an air dryer or a drum dryer.

  Further, from the viewpoint of rubber processability, it is possible to shorten the input relaxation time. However, the natural rubber is partially deproteinized so that the branch point is selectively cut, and the rubber composition It greatly contributes to the reduction of the stress relaxation time and can exhibit excellent workability.

In the present invention, the stress relaxation time of natural rubber is defined by the relationship with the ML _{1 + 4} value at the time of Mooney viscosity measurement, and preferably satisfies both the following formulas (A) and (B).
40 ≦ ML _{1 + 4} ≦ 100 (A)
T ₈₀ <0.0035exp (ML _{1 + 4} /8.2)+20 (B)
[Where ML _{1 + 4} is the Mooney viscosity measured value at 100 ° C., T ₈₀ is the time (seconds) required to stop the rotor rotation immediately after ML _{1 + 4} measurement and the ML _{1 + 4} value is reduced by 80%. ). ]

  Furthermore, the constant viscosity effect can be improved by containing the hydrazide compound in the natural rubber.

  Thus, the above-mentioned natural rubber having a specific total nitrogen content obtained through a specific treatment, combined with a specific sulfenamide vulcanization accelerator described later, imparts excellent processability to the rubber composition. be able to.

[Rubber component]
The rubber composition of the present invention contains the natural rubber as a rubber component. The specific natural rubber is desirably contained in 100% by mass of the rubber component in an amount of at least 5% by mass, preferably 10% by mass or more. If it is less than 5% by mass, a rubber composition having desired physical properties may not be obtained.

  Examples of the rubber component used in combination with the specific natural rubber include normal natural rubber and diene synthetic rubber. Examples of the diene synthetic rubber include styrene-butadiene copolymer (SBR) and polybutadiene rubber (BR). , Polyisoprene rubber (IR), butyl rubber (IIR), ethylene-propylene copolymer, and mixtures thereof. Of these, polyisoprene rubber is preferred from the viewpoint of improving processability.

[Sulfenamide vulcanization accelerator]
The sulfenamide vulcanization accelerator represented by the above formula (I) used in the present invention is a vulcanization equivalent to DCBS which is a conventional sulfenamide vulcanization accelerator represented by the following formula (X). It has a delay effect, can effectively suppress an increase in Mooney viscosity, and can secure a suitable Mooney scorch time. Moreover, it is excellent in adhesion durability in direct vulcanization adhesion with a metal reinforcing material such as a steel cord, and can be suitably used for a rubber composition for coating a thick rubber product.

In the present invention, R ¹ in the sulfenamide vulcanization accelerator represented by the above formula (I) represents a branched alkyl group having 3 to 12 carbon atoms. When R ¹ is a branched alkyl group having 3 to 12 carbon atoms, the sulfenamide-based vulcanization accelerator has good vulcanization acceleration performance and can improve adhesion performance.

Specific examples of R ¹ include isopropyl, isobutyl, triisobutyl, sec-butyl, tert-butyl, isoamyl (isopentyl), neopentyl, tert-amyl (tert-pentyl). , Isohexyl group, tert-hexyl group, isoheptyl group, tert-heptyl group, isooctyl group, tert-octyl group, isononyl group, tert-nonyl group, isodecyl group, tert-decyl group, isoundecyl group, tert-undecyl group, isododecyl Group, tert-dodecyl group and the like. Among these, a tert-alkyl group having 1 to 12 carbon atoms is preferable from the viewpoint of obtaining a suitable Mooney scorch time, and in particular, a tert-butyl group, a tert-amyl group (tert-pentyl group), A tert-dodecyl group and a triisobutyl group are preferable, and among them, a tert-butyl group is preferable because it is economically excellent from the viewpoint of synthesis and raw material acquisition.

  In the sulfenamide-based vulcanization accelerator represented by the above formula (I), n represents 0 or 1, and is preferably 0 from the viewpoint of effects such as ease of synthesis and raw material costs. X in the formula (I) represents an integer of 1 or 2. When x is 3 or more, the reactivity becomes too high, so that the stability of the sulfenamide vulcanization accelerator is lowered and workability may be deteriorated.

These are presumed to be because the more Moony scorch time tends to be imparted as the bulky group exists in the vicinity of —N— adjacent to R ¹ . Therefore, for example, when R ¹ in the above formula (I) is a tert-butyl group and n is 0, R ¹ is a cyclohexyl group, and in the vicinity of —N— as compared with DCBS where n is 0 It is considered that the former is bulkier and can provide a more preferable Mooney scorch time.

In the present invention, R ² in the sulfenamide-based vulcanization accelerator represented by the above formula (I) represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. If R ² is a straight chain having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms, the sulfenamide-based vulcanization accelerator has good vulcanization acceleration performance and also improves adhesion performance. be able to.

Specific examples of R ² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-amyl group (n-pentyl group). ), Isoamyl group (isopentyl group), neopentyl group, tert-amyl group (tert-pentyl group), n-hexyl group, isohexyl group, n-heptyl group, isoheptyl group, n-octyl group, iso-octyl group, nonyl Group, isononyl group, decyl group, undecyl group, dodecyl group and the like. Among these, from the viewpoint of effects such as ease of synthesis and raw material costs, a straight chain having 1 to 8 carbon atoms or a branched alkyl group having 3 to 8 carbon atoms is preferable, and a straight chain having 1 to 6 carbon atoms is more preferable. It is more preferably a chain or a branched alkyl group having 3 to 6 carbon atoms, and examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a sec-butyl group. In particular, the straight chain alkyl group having the carbon number is more preferable than the branched alkyl group having the carbon number in that a suitable Mooney scorch time can be obtained and high steel cord adhesion can be obtained. If this is a branched alkyl group, the vulcanization is further delayed, so that the productivity may be lowered, or the adhesiveness may be lowered when compared with the same carbon number as that of the linear alkyl group. Among these, a methyl group, an ethyl group, and an n-propyl group are most desirable.

Therefore, if R ² in the above formula (I) is a conventional sulfenamide vulcanization accelerator such as H, the vulcanization speed may be too high and good adhesiveness tends not to be obtained. is there. Further, when R ² is a conventional sulfenamide vulcanization accelerator such as a cyclohexyl group or a long chain group outside the above range, the vulcanization rate tends to be too slow. .

Among the sulfenamide vulcanization accelerators mentioned above, the Mooney scorch time does not become too fast, does not cause scorching of rubber during processing, avoids deterioration in workability, and can also maintain good adhesion. The preferred embodiments are further summarized in order from the preferred embodiments. Specifically, 1) R ¹ in the above formula (I) is a tert-alkyl group, and R ² is a linear alkyl having 1 to 10 carbon atoms. Or a branched alkyl group having 3 to 10 carbon atoms and n = 0, 2) R ¹ in the above formula (I) is a tert-alkyl group, and R ² is a straight chain having 1 to 6 carbon atoms. A chain alkyl group or a branched alkyl group having 3 to 6 carbon atoms, wherein n is 0 or 1, 3) R ¹ in the above formula (I) is a tert-alkyl group, and R ² is 1 carbon atom. A linear alkyl group of -6 or a branched alkyl group of 3-6 carbon atoms Ri, those wherein n = 0, 4) in which R ¹ in the above formula (I) is tert- alkyl group, R ² is either a methyl group, an ethyl group or n- propyl group,, n = A value of 0 is preferable (the descending order is a suitable sulfenamide-based vulcanization accelerator).

In the sulfenamide vulcanization accelerator represented by the above formula (I), R ¹ is a functional group other than a branched alkyl group having 3 to 12 carbon atoms (for example, n-octadecyl group, etc.) or carbon number. Is a branched alkyl group having more than 12, R ² is a linear group having 1 to 10 carbon atoms or a functional group other than a branched alkyl group (eg, n-octadecyl group) or a linear chain having more than 10 carbon atoms. Or when it is a branched alkyl group, and when n is 2 or more, the intended effect of the present invention cannot be fully exerted, and the Mooney scorch time is delayed beyond the preferred range, and the vulcanization time is longer than necessary. If the length is too long, productivity and adhesiveness may decrease, or vulcanization performance and rubber performance as an accelerator may decrease. Further, when x is 3 or more, it is not preferable in terms of stability.

  In the present invention, typical examples of the sulfenamide-based vulcanization accelerator represented by the above formula (I) include N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N- Ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS), Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide, N-isopropyl-Nt-butylbenzothiazole -2-sulfenamide, Nn-butyl-Nt-butylbenzothiazole-2-sulfenamide (BBBS), N-isobutyl-Nt-butylbenzothiazole-2-sulfenamide, N- sec-Butyl-Nt-butylbenzothiazole-2-sulfenamide, N-methyl-N-isoamylbenzothiazole-2-sulfenamide Amide (BMBS), N-ethyl-N-isoamylbenzothiazole-2-sulfenamide (BEBS), Nn-propyl-N-isoamylbenzothiazole-2-sulfenamide, N-isopropyl-N-isoamylbenzo Thiazole-2-sulfenamide, Nn-butyl-N-isoamylbenzothiazole-2-sulfenamide (BBBS), N-isobutyl-N-isoamylbenzothiazole-2-sulfenamide, N-sec-butyl -N-isoamylbenzothiazole-2-sulfenamide, N-methyl-N-tert-amylbenzothiazole-2-sulfenamide (BMBS), N-ethyl-N-tert-amylbenzothiazole-2-sulfen Amide (BEBS), Nn-propyl-N-ter -Amylbenzothiazole-2-sulfenamide, N-isopropyl-N-tert-amylbenzothiazole-2-sulfenamide, Nn-butyl-N-tert-amylbenzothiazole-2-sulfenamide (BBBS ), N-isobutyl-N-tert-amylbenzothiazole-2-sulfenamide, N-sec-butyl-N-tert-amylbenzothiazole-2-sulfenamide, N-methyl-N-tert-heptylbenzo Thiazole-2-sulfenamide (BMBS), N-ethyl-N-tert-heptylbenzothiazole-2-sulfenamide (BEBS), Nn-propyl-N-tert-heptylbenzothiazole-2-sulfene Amide, N-isopropyl-N-tert-heptylben Zothiazole-2-sulfenamide, Nn-butyl-N-tert-heptylbenzothiazole-2-sulfenamide (BBBS), N-isobutyl-N-tert-heptylbenzothiazole-2-sulfenamide, N -Sec-butyl-N-tert-heptylbenzothiazole-2-sulfenamide and the like. These may be used alone or in combination of two or more.

  Among these, N-methyl-Nt-butylbenzothiazole-2-sulfenamide (BMBS), N-ethyl-Nt-butyl is the longest Mooney scorch time and excellent adhesion performance. Benzothiazole-2-sulfenamide (BEBS) and Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide are preferred.

  These sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazole sulfenamide (TBBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), dibenzothiazolyl disulfide (MBTS). ) And other general-purpose vulcanization accelerators.

  Content of the said sulfenamide type | system | group vulcanization accelerator is 0.1-10 mass parts with respect to 100 mass parts of rubber components, Preferably it is 0.5-5.0 mass parts, More preferably, it is 0.8-2. .5 parts by mass. If the content of the vulcanization accelerator is less than 0.1 parts by mass, the vulcanization may not be sufficiently performed. On the other hand, if it exceeds 10 parts by mass, bloom may be a problem, which is not preferable.

  Preferred examples of the method for producing the sulfenamide-based vulcanization accelerator include the following methods.

  That is, N-chloroamine prepared in advance by reaction of a corresponding amine and sodium hypochlorite and bis (benzothiazol-2-yl) disulfide are reacted in an appropriate solvent in the presence of an amine and a base. If an amine is used as the base, neutralize and return to the free amine, then subject to appropriate post-treatment such as filtration, washing with water, concentration and recrystallization according to the properties of the resulting reaction mixture. Sulfenamide is obtained.

  Examples of the base used in this production method include starting amines used in excess, tertiary amines such as triethylamine, alkali hydroxides, alkali carbonates, alkali bicarbonates, sodium alkoxides, and the like. In particular, the reaction is carried out using excess raw material amine as a base or tertiary amine triethylamine, neutralizing the hydrochloride formed with sodium hydroxide, taking out the target product, and then removing the amine from the filtrate. A method of reuse is desirable.

As the solvent used in this production method, alcohol is desirable, and methanol is particularly desirable.
For example, in N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS), an aqueous sodium hypochlorite solution was added dropwise to Nt-butylethylamine at 0 ° C. or lower and the oil layer was stirred for 2 hours. Was sorted. Bis (benzothiazol-2-yl) disulfide, Nt-butylethylamine and the oil layer described above were suspended in methanol and stirred for 2 hours under reflux. After cooling, the solution is neutralized with sodium hydroxide, filtered, washed with water, concentrated under reduced pressure, and recrystallized to obtain the target BEBS (white solid).

[sulfur]
Sulfur used in the present invention acts as a vulcanizing agent, and the content thereof is 0.3 to 10 parts by mass, preferably 1.0 to 7.0 parts by mass, with respect to 100 parts by mass of the rubber component. More preferably, the amount is 3.0 to 7.0 parts by mass. If the sulfur content is less than the above lower limit value, vulcanization may not be achieved sufficiently. On the other hand, if the sulfur content exceeds the upper limit value, the aging performance of the rubber may be deteriorated.

[Rubber composition]
In addition to the rubber component containing the natural rubber, the sulfenamide vulcanization accelerator and sulfur, the rubber composition of the present invention preferably further contains a filler. Although it does not specifically limit as a filler, The thing normally used for rubber industries, such as carbon black, a silica, an alumina, aluminum hydroxide, clay, a calcium carbonate, can be used.

When carbon black is blended, the nitrogen adsorption specific surface area (N ₂ AS) is 80 m ² / g or more, preferably 100 m ² / g or more, or the DBP oil absorption amount (100 parts by mass of the rubber component including the natural rubber) It is desirable to blend carbon black having an n-dibutyl phthalate oil absorption) of 110 ml / 100 g or less, preferably 90 ml / 100 g or less in an amount of 20 to 100 parts by mass.

That is, when natural rubber that has been partially deproteinized in the present invention is used, carbon black having a fine particle diameter of nitrogen adsorption specific surface area of 80 m ² / g or more, or DBP oil absorption of 100 ml / 100 g or less. Even when carbon black with a low structure is blended, the dispersibility of carbon black can be improved compared to the case of using conventional natural rubber, and not only the processability of the rubber composition but also wear resistance and low Physical properties such as loss (low heat generation) can be greatly improved.

  There is no restriction | limiting in particular as said carbon black, Arbitrary things can be selected and used from what is conventionally used as a reinforcing filler of rubber | gum. Specific examples include FEF, SRF, HAF, ISAF, and SAF. From the point of wear resistance, HAF, ISAF, and SAF are preferable.

  Moreover, when mix | blending a silica, it is preferable to mix | blend in the quantity of 20-80 mass parts with respect to 100 mass parts of rubber components containing the said natural rubber. That is, when silica is blended with the partially deproteinized natural rubber, the dispersibility of the silica and the shrinkage of the blend can be greatly improved compared to the conventional natural rubber. Not only the workability of the object but also the physical properties such as wear resistance and low heat generation can be remarkably improved.

  The silica is not particularly limited, but wet silica, dry silica, and colloidal silica are preferable. Such fillers can be used alone or in admixture of two or more.

  The rubber composition of the present invention includes various chemicals usually used in the rubber industry, for example, process oil, anti-aging agent, scorch preventing agent, zinc white, stearin as long as the object of the present invention is not impaired. An acid etc. can be contained.

  The rubber composition of the present invention can be produced by kneading each of the above components with a Banbury mixer, a kneader or the like.

[tire]
The rubber composition in the present invention is particularly suitably used as tire rubber, and can be applied to all tire members such as tread rubber (including cap rubber and base rubber), side rubber, ply rubber, and bead filler rubber.

  Especially as a tire member, it is used suitably for a tire case member and a tire tread. Here, the tire case member includes all rubber members except for the tread rubber, but the tire inner member is particularly preferable, for example, belt coating rubber, carcass ply coating rubber, squeegee rubber between plies, and between tread and belt. A cushion rubber, a bead filler, etc. are mentioned.

  Since the rubber composition of the present invention has remarkably improved processability, when applied to a tire case member, for example, a belt or a carcass ply rubber coating rubber, the cord separation property and rubber / cord adhesion in the tire after running Products that have excellent physical properties such as properties and rubber mechanical properties (such as retention of elongation at break) can be manufactured efficiently and easily, contributing to improved productivity. Become.

  Moreover, when the rubber composition in the present invention is applied to a tire tread, the wear resistance, low heat generation property, tear resistance and the like of the tread rubber can be remarkably improved.

  The rubber composition of the present invention can be applied to applications such as vibration-proof rubber, belts, hoses and other industrial products in addition to tires.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
The measurement of the total nitrogen content in natural rubber, the Mooney viscosity (ML _{1 + 4} ) and Mooney scorch time evaluation method, and the stress relaxation time (T ₈₀ ) measurement were performed according to the following methods.

<Measurement of total nitrogen content>
The total nitrogen content was measured by the Kjeldahl method and determined as a ratio (mass%) to the total amount.

<Evaluation method of Mooney viscosity and Mooney scorch time>
This was performed according to JIS K 6300-1: 2001.
The evaluation of Mooney scorch time was expressed as an index with the value of Comparative Example 1 being 100. The smaller the value of Mooney viscosity (ML _{1 + 4} ), the better the workability during kneading, and the greater the Mooney scorch time, the better the workability after kneading.

<Measurement method of stress relaxation time>
Immediately after measuring the Mooney viscosity (ML _{1 + 4} ), the rotor rotation was stopped, and the time (seconds) required until the Mooney viscosity value was reduced by 80% was measured. It shows that it is excellent in workability, so that the value of stress relaxation time ( _T80 ) is small.

[Production Example 1: Synthesis of N-methyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 1)]
To 14.1 g (0.162 mol) of Nt-butylmethylamine, 148 g of a 12% aqueous sodium hypochlorite solution was added dropwise at 0 ° C. or lower, and after stirring for 2 hours, the oil layer was separated. Bis (benzothiazol-2-yl) disulfide (39.8 g, 0.120 mol), Nt-butylmethylamine (24.3 g, 0.240 mmol) and the oil layer described above were suspended in 120 ml of methanol and refluxed. Stir for 2 hours. After cooling, the solution was neutralized with 6.6 g (0.166 mol) of sodium hydroxide, filtered, washed with water, concentrated under reduced pressure, and then recrystallized to obtain 46.8 g (yield 82%) of the target BMBS as a white solid. (Melting point 56-58 ° C.).

^{1 H-NMR (400MHz, CDCl} 3) δ = 1.32 (9H, s, CH 3 (t- butyl)), 3.02 (3H, s , CH 3 ( methyl)), 7.24 (1H, m), 7.38 (1H, m), 7.77 (1H, m), 7.79 (1H, m).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 27.3, 41.9, 59.2, 120.9, 121.4, 123.3, 125.7, 135.0, 155.5, 180. 8).
Mass spectrometry (EI, 70 eV) m / z; 252 (M ⁺ ), 237 (M ⁺ -CH ₃ ), 223 (M ⁺ -C ₂ H ₆ ), 195 (M ⁺ -C ₄ H ₉ ), 167 ( _{^{M + -C 5 H 12 N)}} , 86 (M + -C 7 H 4 NS 2).

[Production Example 2: Synthesis of N-ethyl-Nt-butylbenzothiazole-2-sulfenamide (BEBS, vulcanization accelerator 2)]
The same procedure as in Example 1 was carried out using 16.4 g (0.162 mol) of Nt-butylethylamine instead of Nt-butylmethylamine, and 41.9 g (yield 66%) of BEBS as a white solid ( Obtained as a melting point of 60 to 61 ° C.).
The spectrum data of the obtained BEBS is shown below.

^{1 H-NMR (400MHz, CDCl} 3) δ = 1.29 (t, 3H, J = 7.1Hz, CH 3 ( ethyl)), 1.34 (s, 9H , CH 3 (t- butyl)), 2.9-3.4 (br-d, CH ₂ ), 7.23 (1H, m), 7.37 (1H, m), 7.75 (1H, m), 7.78 (1H, m ).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 15.12, 28.06, 47.08, 60.41, 120.70, 121.26, 123.23, 125.64, 134.75, 154. 93, 182.63.
Mass spectrometry (EI, 70 eV): m / z; 251 (M ⁺ —CH ₄ ), 167 (M ⁺ —C ₆ H ₁₄ N), 100 (M ⁺ —C ₇ H ₅ NS ₂ ): IR (KBr, cm < ^-1 >): 3061, 2975, 2932, 2868, 1461, 1429, 1393, 1366, 1352, 1309, 1273, 1238, 1198, 1103, 1022, 1011, 936, 895, 756, 727.

[Production Example 3: Synthesis of Nn-propyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 3)]
The same procedure as in Example 1 was carried out using 18.7 g (0.162 mol) of Nn-propyl-t-butylamine instead of Nt-butylmethylamine, and Nn-propyl-Nt-butylbenzo Thiazole-2-sulfenamide was obtained as a white solid (melting point 50-52 ° C.).

^{1 H-NMR (400MHz, CDCl} 3) δ = 0.92 (t, J = 7.3Hz, 3H), 1.34 (s, 9H), 1.75 (br, 2H), 3.03 (brd , 2H), 7.24 (t, J = 7.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7 .79 (d, J = 7.5 Hz, 1H).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 11.7, 23.0, 28.1, 55.3, 60.4, 120.7, 121.3, 123.3, 125.7, 134. 7, 154.8, 181.3.

[Production Example 4: Synthesis of Ni-propyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 4)]
The same procedure as in Example 1 was carried out except that 18.7 g (0.162 mol) of Ni-propyl-t-butylamine was used instead of Nt-butylmethylamine, and Ni-propyl-Nt-butylbenzo was used. Thiazole-2-sulfenamide was obtained as a white solid (melting point 68-70 ° C.).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 1.20-1.25 (dd, (1.22 ppm: J = 6.4 Hz, 1.23 ppm: J = 6.4 Hz) 6H), 1.37 ( s, 9H), 3.78 (m, J = 6.3 Hz, 1H), 7.23 (t, J = 7.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7.79 (d, J = 7.5 Hz, 1H).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 22.3, 23.9, 29.1, 50.6, 61.4, 120.6, 121.2, 123.2, 125.6, 134. 5, 154.5, 183.3.

[Production Example 5: Synthesis of N, N-di-i-propylbenzothiazole-2-sulfenamide (vulcanization accelerator 5)]
N, N-di-i-propylbenzothiazole-2 was prepared in the same manner as in Example 1 except that 16.4 g (0.162 mol) of N-di-i-propylamine was used instead of Nt-butylmethylamine. -Sulfenamide was obtained as a white solid (melting point 57-59 ° C).

^{1 H-NMR (400MHz, CDCl} 3) δ = 1.26 (d, J = 6.5Hz, 12H), 3.49 (dq, J = 6.5Hz, 2H), 7.24 (t, J = 7.0 Hz, 1H), 7.37 (t, J = 7.0 Hz, 1H), 7.75 (d, J = 8.6 Hz, 1H), 7.79 (d, J = 8.6 Hz, 1H) ).
¹³ C-NMR (100 MHz, CDCl ₃ ) δ = 21.7, 22.5, 55.7, 120.8, 121.3, 123.4, 125.7, 134.7, 155.1, 182. 2.
Mass spectrometry (EI, 70 eV), m / z 266 (M ⁺ ), 251 (M ⁺ −15), 218 (M ⁺ −48), 209 (M ⁺ −57), 182 (M ⁺ −84), 167 ( M ^<+>- 99), 148 (M ^<+ > ^- 118), 100 (M ^<+ > ^- 166: base).

[Production Example 6: Synthesis of Nn-butyl-Nt-butylbenzothiazole-2-sulfenamide (vulcanization accelerator 6)]
The same procedure as in Example 1 was carried out using 20.9 g (0.162 mol) of Nt-butyl-n-butylamine instead of Nt-butylmethylamine, and 42.4 g (yield 60%) of BBBS was used. Obtained as a white solid (mp. 55-56 ° C.).

¹ H-NMR (400 MHz, CDCl ₃ ) δ = 0.89 (3H, t, J = 7.32 Hz, CH ₃ (n-Bu)), 1.2-1.4 (s + m, 11H, CH ₃ ( t-butyl) + CH ₂ (n-butyl)), 1.70 (br.s, 2H, CH ₂ ), 2.9-3.2 (br.d, 2H, N—CH ₂ ), 7.23 (1H, m), 7.37 (1H, m), 7.75 (1H, m), 7.78 (1H, m).
^{13 C-NMR (100MHz, CDCl} 3) δ = 14.0,20.4,27.9,31.8,53.0,60.3,120.6,121.1,123.1,125. 5, 134.6, 154.8, 181.2.
Mass spectrometry (EI, 70 eV), m / z 294 (M ⁺ ), 279 (M ⁺ —CH ₃ ), 237 (M ⁺ —C ₄ H ₉ ), 167 (M ⁺ —C ₈ H ₁₈ N), 128 ( M ⁺ -C ₇ H ₄ NS ₂ ): IR (neat): 1707 cm ⁻¹ , 3302 cm ⁻¹ .

[Production Example 7: Production of natural rubber (NR-1)]
(I) Peptide bond decomposition process of natural rubber latex Anionic surfactant [“Demol” manufactured by Kao Co., Ltd., surfactant concentration is 2.5 mass%] 24.7 ml, protease (“Alkalase manufactured by Novozymes”) A solution was prepared by adding 0.06 g of 2.5 L, type DX ") and mixing.
Next, 1000 g of a natural rubber latex having a solid content of 20% by mass was kept constant at 40 ° C. in a water bath, and the solution was added dropwise while stirring, and the stirring was continued at the same temperature for 5 hours. Got.

(Ii) Coagulation / Drying Step The rubber obtained by acid coagulation is passed through a drum dryer set at 130 ° C. five times, and then dried at 40 ° C. for 8 hours in a vacuum dryer, and natural rubber (NR -1) was produced.

[Production Example 8: Production of natural rubber (NR-2)]
A natural rubber latex (B) was obtained in the same manner as in Production Example 7 except that peptidase (“Devitrase” manufactured by Soho Tsusho Co., Ltd.) was used instead of protease. Then, natural rubber (NR-2) was obtained by acid coagulation and drying. Manufactured.

[Examples 1-7]
Table 1 shows the natural rubber (NR-1 or NR-2) obtained in the above production example, the vulcanization accelerator, sulfur, and other compounding agents obtained in the above production example using a 2200 ml Banbury mixer. An unvulcanized rubber composition was prepared by kneading and mixing according to the formulation, and the Mooney viscosity, Mooney scorch time, and stress relaxation time were measured according to the methods described above. The results are shown in Table 1.

[Comparative Example 1]
Example except that ordinary natural rubber (NR-3) (RSS # 3 kneaded rubber: total nitrogen content 0.42% by mass) was used, and the conventional vulcanization accelerator A (DCBS) was used. A rubber composition was prepared according to 1 and measured for each item. The results are shown in Table 1.

[Comparative Example 2]
A rubber composition was prepared according to Example 1 and measured for each item, except that a conventional vulcanization accelerator (DCBS) was used. The results are shown in Table 1.

* 1: Carbon black N326: manufactured by Qingdao Yadong Machine Co., Ltd. * 2: N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine (NOCRACK 6C, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 3: N, N'-dicyclohexyl-2-benzothiazylsulfenamide (Noxeller DZ, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

  According to the results in Table 1, Examples 1 to 7 are all Comparative Example 1 in which a conventional natural rubber and a conventional vulcanization accelerator are used in combination, and a Comparative Example in which only a conventional vulcanization accelerator is used. Compared to 2, it can be seen that good Mooney viscosity and Mooney scorch time are exhibited, stress relaxation time is increased, and workability is improved.

Claims (12)

A rubber component comprising a natural rubber obtained by deproteinizing a natural rubber latex and adjusted so that the total nitrogen content in the natural rubber is 0.12 to 0.30% by mass; A rubber composition comprising a sulfenamide vulcanization accelerator represented by formula (I) and sulfur;

(In formula (I), R ¹ represents a branched alkyl group having 3 to 12 carbon atoms, and R ² represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. Represents 0 or 1, and x represents 1 or 2.)   The rubber composition according to claim 1, wherein the natural rubber is obtained by coagulating a natural rubber latex after deproteinization treatment without centrifuging a non-rubber component and drying the natural rubber latex. The rubber according to claim 1 or 2, wherein the natural rubber has a Mooney viscosity (ML _{1 + 4} ) and a stress relaxation time (T ₈₀ ) satisfying the following formulas (A) and (B): Composition;
40 ≦ ML _{1 + 4} ≦ 100 (A)
T ₈₀ <0.0035exp (ML _{1 + 4} /8.2)+20 (B)
[Where ML _{1 + 4} is the Mooney viscosity measured value at 100 ° C., T ₈₀ is the time (seconds) required to stop the rotor rotation immediately after ML _{1 + 4} measurement and the ML _{1 + 4} value is reduced by 80%. ). ].   The rubber composition according to any one of claims 1 to 3, wherein the sulfenamide vulcanization accelerator is contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to any one of claims 1 to 4, wherein the sulfur component is contained in an amount of 0.3 to 10 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition according to claim 1, wherein in the formula (I), R ¹ is a tert-alkyl group and n is 0. In the formula (I), R ¹ is a tert-alkyl group, and R ² is a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms. A rubber composition according to any one of the above. In the formula (I), R ¹ is a tert-alkyl group, R ² is a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms, and n is 0. Item 8. The rubber composition according to any one of Items 1 to 7. The formula (I), wherein R ¹ is a tert-alkyl group, R ² is a methyl group, an ethyl group or an n-propyl group, and n is 0. Rubber composition.   The rubber composition according to any one of claims 1 to 9, wherein the rubber component contains a polyisoprene rubber.   The rubber composition according to any one of claims 1 to 10, comprising the natural rubber in an amount of 5% by mass or more in 100% by mass of the rubber component.   A tire comprising the rubber composition according to any one of claims 1 to 11 as a tire member.